1. Field of the Invention
This invention relates to a burner device and a method of making the burner device which is suited to be used as a heating source of a water heater device.
2. Description of Prior Art
In a burner device used for a water heating apparatus, a second burner has a second fire hole provided in a manner to sandwich a first fire hole of a first burner as shown in Japanese Patent Provisional Publication No. 3-263505. In such a water heating apparatus, a row array of the burner devices are arranged at regular intervals in which an air-fuel mixture is supplied to the first fire hole and the second fire hole through an individual nozzle.
The first fire hole predominantly burns an air-rich fuel which is leaner than a stoichimetric air-fuel ratio, while the second fire hole burns a fuel-rich mixture which is richer than the stoichimetric air-fuel ratio. This makes it possible to substantially hold a uniform air-fuel mixing ratio so as to reduce an emission of nitric oxide (NOx) to 40.about.60 ppm compared to an existing art in which the emission is around 120 ppm. It is also possible to burn the fuel-rich mixture at the first fire hole, and burning the air-rich fuel at the second fire hole to reduce the emission of nitric oxide (NOx).
In this type of the water heating apparatus, however, three suction holes and three nozzles are required to supply the air-fuel mixture to a row of three fire holes. This requires complicated procedures to adjust the air-fuel ratio due to dimensional variations of assembling elements so as to make the whole structure more complex and expensive.
Therefore, it is one object of the invention to provide a burner device which is capable of simplifying air-fuel supplying system and readily adjusting the air-fuel ratio to reduce the manufacturing cost.
It is another object of the invention to provide method of making a burner device which is capable of being readily manufactured and thus reduce the manufacturing cost by enclosing a metal plate around a first burner to form a second fire hole.
It is still another object of the invention to provide a method of making a burner device which is capable of uniformly distributing the air-fuel mixture which is supplied to two second fire holes provided at both sides of the first burner.
It is one object of the invention to provide a burner device which is capable of reducing a level of noise by dividing the first fire hole into flame holes.
These and other objects and advantages of the invention will be apparent upon reference to the following specification, attendant claims and drawings.